The Question
Blade pitch and drivetrain gearing both change how much of the wind's energy a small turbine converts into electrical power — but changing them at the same time makes it impossible to tell which one is responsible for a result. This project holds one variable fixed while sweeping the other, across a range of wind speeds, to isolate the effect of each.
Method
Each trial holds wind speed steady at a target value, records rotor RPM, and measures voltage and current across a fixed load. Power is calculated as V × I. Two test blocks isolate one variable each:
Gear ratio held at 3:1. Fin angle tested at 10°, 20°, and 30°, each across four wind speeds (3–9 m/s).
Fin angle held at 20° (the best performer from Block A). Gear ratio tested from 2:1 to 5:1, each across three wind speeds (4–8 m/s).
Results
Block A · gear ratio fixed at 3:1
Block B · fin angle fixed at 20°
20° outperformed 10° and 30° at every wind speed tested — consistent with a moderate pitch balancing lift and drag better than a shallower or steeper angle.
A 4:1 gear ratio produced the most power at every wind speed tested among the ratios tried (2:1–5:1), suggesting the generator's optimal RPM range sits above what 2:1 and 3:1 deliver at these wind speeds.
What I Learned / Next Steps
- Holding one variable constant while sweeping the other made it possible to attribute each change in output to a single cause — the biggest methodology shift from my earlier, less controlled tests.
- Both sweeps were coarse. The next round should test fin angles between 15° and 25° and gear ratios between 3.5:1 and 4.5:1 to find the actual peak rather than the best of a few options.
- Power alone doesn't account for how much wind energy was available at each speed. Adding a calculated efficiency metric (output power ÷ theoretical wind power) would make trials at different wind speeds directly comparable.
- A mounted anemometer and a data-logging microcontroller would replace manual fan-speed estimates and reduce recording error between trials.
Full Data
Complete Trial Log
All 24 trials, including RPM and raw voltage/current readings behind every chart above.
View Spreadsheet →Rig Photos
Photos of the build referenced in the Method section.